I'm thinking Affleck will win another before Damon, but I don't know if it will be for Argo.
I think the movie looks great, but will the Oscars really reward it. I can see nominations, including possibly director, but I don't see any wins, atm.
I see that Affleck didn't write the script for this one, but if the movie is loved enough for the Academy to give it wins, Affleck has a shot in director. But I still think he is more likely to win another writing Oscar than one for directing or acting. He got close to screenplay noms for his previous two films.
Usually if you have a writer-director nominated for both categories at the Oscars, they will reward them in writing. Ex: Alexander Payne, The Coen Brothers (Fargo), Jane Campion, Sofia Coppola, Neil Jordan (The Crying Game), and Woody Allen just last year. That's where my thinking is coming from.
But like I said, if the Academy really loves the movie and wants to reward Affleck, it will have to be for directing this time or even Best Picture since he's a producer.